10.7.2 Back to My Mac complaining about router settings

I try to enable Back to My Mac, and it complains that performance won't be very good unless I enable UNNP or NAT-PMP on my router. After doing some Googling, I determined that, since I have service from AT&T U-Verse, neither of these technologies is supported by my router! My network setup looks like this:
What should I do, if anything? I've already looked at the router's user manual and poked around in the settings web interface for it. No dice.

Hey, at least I'm not alone! I haven't tested Back to my Mac yet, and can't right now due to my MBA refusing to install Lion... but that's an issue for another thread.

Anyway, how is your network configured? If you have 2 routers connected to each other, that may be the source of your problem - Mac OS X will only see the inner router, even if the outer router is correctly configured, as yours appears to be.